Berberine sensitizes nasopharyngeal carcinoma cells to radiation through inhibition of Sp1 and EMT.

Nasopharyngeal carcinoma (NPC) is a tumor of epithelial origin with radiotherapy as its standard treatment. However, radioresistance remains a critical issue in the treatment of NPC. This study aimed to investigate the effect of berberine on the proliferation, cell cycle regulation, apoptosis, radioresistance of NPC cells and whether specificity protein 1 (Sp1) is a functional target of berberine. Our results showed that treatment with berberine reduced the proliferation and viability of CNE-2 cells in a dose- and time‑dependent manner. Berberine induced cell cycle arrest in the G0/G1 phase and apoptosis. In CNE-2 cells exposed to gamma‑ray irradiation, berberine reduced cell viability at various concentrations (25, 50, 75 and 100 µmol/l). Berberine significantly decreased mRNA and protein expression of Sp1 in the CNE-2 cells. Mithramycin A, a selective Sp1 inhibitor, enhanced the radiosensitivity and the rate of apoptosis in the CNE-2 cells. Berberine inhibited transforming growth factor-β (TGF-β)-induced tumor invasion and suppressed epithelial-to-mesenchymal transition (EMT) process, as evidenced by increased E-cadherin and decreased vimentin proteins. Sp1 may be required for the TGF-β1-induced invasion and EMT by berberine. In conclusion, berberine demonstrated the ability to suppress proliferation, induce cell cycle arrest and apoptosis, and enhance radiosensitivity of the CNE-2 NPC cells. Sp1 may be a target of berberine which is decreased during the radiosensitization of berberine.